I recently created a WCF service (dll) and a service host (exe). I know my WCF service is working correctly since I am able to successfully add the service to WcfTestClient.
Today i ran into same issue, posting here my mistake and correction of it so that it may help someone.
While Re-structuring code, I had actually changed Service class and IService names and changed ServiceHost to point to this new Service class name (as shown in code snippet) but in my host applications App.Config file i was still using old Service class name.(refer config section's name field in below snippet)
Here is the code snippet,
ServiceHost myServiceHost = new ServiceHost(typeof(NewServiceClassName));
and in App.config file under section services i was referring to old serviceclass name , changing it to New ServiceClassName fixed issue for me.